1. Field of the Invention
The present invention relates to a connection device and related method, and more particularly, to a connection device capable of mixing an RGB graphics signal and a YUV video signal and related method.
2. Description of the Prior Art
In computer systems, input formats of video signals and graphics signals are typically different. The input format of video signals is luminance-bandwidth-chrominance (YUV or YCbCr) or red-green-blue (RGB). However, the input format of graphics signals is RGB. If a display device, such as a liquid crystal display (LCD), cathode ray tube (CRT) or plasma display panel (PDP) display, is compatible with a computer the output format of the video signal and the graphics signal are both RGB. If the display is a TV, the output format of the video signal and the graphics signal must be YUV (or YCbCr) to comply with the format of TV signals. Therefore, in the prior art, if the input format of the video signal is YUV (or YCbCr) and the display is a TV, the YUV video signal must be first transformed into an RGB video signal, mixed with an RGB graphics signal, transformed into a YUV signal, and then output to the TV. During the process of transformation, distortion (such as color distortion) of the video signal can occur.
Please refer to FIG. 1. FIG. 1 is a diagram of a connection device 100 according to the prior art. The connection device 100 comprises a first video transforming module 120, a second video transforming module 140, a mixing module 130, a TV output interface 110, an LCD output interface 112, a CRT output interface 114, and a PDP output interface 116. The first video transforming module 120 is utilized for transforming a YUV video signal into an RGB video signal. The mixing module 130 is utilized for mixing an RGB graphics signal and the RGB video signal generated by the first video transforming module 120. The second video transforming module 140 is utilized for transforming an RGB signal generated by the mixing module 130 into a YUV signal.
When receiving a YUV video signal, the first video transforming module 120 transforms the YUV video signal into an RGB video signal and outputs the RGB video signal to the mixing module 130. The mixing module 130 is utilized for receiving the RGB video signal and the RGB graphics signal, mixing the two signals and then outputting the mixed signals to an output interface to simultaneously represent the video and graphics signals on a display. If the display, such as an LCD, CRT or PDP display, is compatible with a computer the mixing module 130 directly outputs the mixed RGB signals to the LCD output interface 112, CRT output interface 114 or PDP output interface 116. If the display is a TV, the mixing module 130 outputs the mixed RGB signals to the second video transforming module 140. The second video transforming module 140 transforms the mixed RGB signals into YUV signals and then the YUV signals are output to the TV output interface 110.
As mentioned above, in the prior art connection device 100, the YUV video signal must be transformed into an RGB video signal by the first video transforming module 120. If the display is a TV, the RGB video signal will be transformed back into the YUV video signal by the second video transforming module 140. Then the YUV video signal is output to the TV. Due to the two transformations of the original video signal, distortion (such as color distortion) of the original video signal output to the TV can occur.